Optical disc and method of identifying recording layer

ABSTRACT

An optical disc in which a physical address of each smallest recording unit and a recorded address increase or decrease on first and second recording layers, and a method of identifying the recording layers. Embodiments are provided for discs having first and second recording layers with a same or an opposite track spiral direction. Physical addresses of the smallest recording units and a recorded address are increased or decreased between an inner radius and an outer radius of a recording layer in a manner which enables a reproducing and/or a recording device to more rapidly reproduce and/or record data on the disc. A physical address of the smallest recording units on the first recording layer is made different from a physical address of the smallest recording units on the second recording layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/204,357, filed on Aug. 16, 2005, which is a continuation of U.S.patent application Ser. No. 10/099,946, filed on Mar. 19, 2002,currently pending, which claims the benefit of Korean Application No.2001-18472 filed Apr. 7, 2001 in the Korean Patent Office, thedisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disc and a method ofidentifying a recording layer, and more particularly, to a recordableand/or reproducible optical disc, in which a physical address ofsmallest recording units and an address of the smallest recording unitsrecorded during recording of data on the disc increase or decrease onfirst and second recording layers, and a method of identifying therecording layers without recording information about each recordinglayer.

2. Description of the Related Art

In an optical disc drive, physical identification data (PID) refers toinformation recorded for identifying a physical location on a disc whosedata is to be reproduced. In general, PID is physical sector addressinformation recorded on a recordable and/or reproducible medium on whichdata is recordable and/or reproducible per sector. PID is used to recorddata at an arbitrary position on a disc and to locate the recordingposition. A read-only memory (ROM) disc records addresses by usingpredetermined bits in an ID region of a header area of a sector that isthe smallest unit of data that is recordable on a disc.

Referring to FIG. 1A showing a conventional parallel spiral track dischaving dual layers, first and second layer L0-1 and L1-1 have the sametrack spiral direction. Here, as shown in FIG. 1B, sector addresses onthe first and second layers L0-1 and L1-1 increase from an inner radiusRin of a disc to an outer radius Rout of the disc, respectively. In acase of continuous reproduction, data recorded on the first layer L0-1of the disc is reproduced from the inner radius of the first layer L0-1to the outer radius of the first layer and then data recorded on thesecond layers L1-1 of the disc is reproduced from the inner radius ofthe second layer L1-1 to the outer radius of the second layer L1-1.Because a pickup of a reproduction apparatus must move back toward theinner radius Rin of the disc in order to reproduce data from the secondlayer L1-1 successively after the first layer L0-1, an additional accesstime due to time for this movement as well as a decrease in linearvelocity as shown in FIG. 1 C is required.

To compensate for this, as shown in FIG. 2A, first and second layersL0-1 and L1-1 have opposite spiral directions. Furthermore, sectoraddresses on the first layer L0-1 increase from the inner radius Rin ofthe disc to the outer radius Rout, while sector addresses on the secondlayer L1-1 successively increase from the outer radius Rout to the innerradius Rin, thereby reducing a time taken to access from the first layerL0-1 to the second layer L1-1. This is called an opposite spiral trackpath. In particular, U.S. Pat. No. 5,881,032 discloses an optical discin which sector addresses are arranged for a plurality of recordinglayers.

In a conventional DVD dual layer disc, first and second layers L0 and L1are identifiable using predetermined bits in an ID region of a headerarea at the beginning of a sector that is the smallest unit that can berecorded on the disc. However, if a recordable disc is to storeinformation about sectors and layers in a wobble on a groove track,repeated recording may degrade characteristics of the wobble so that theinformation about sectors or layers is not detectable. For example, aDVD-RAM stores address information including layer information in aheader area in the form of pits before recording data. However, thelayer information is repeatedly recorded in a data identification data(DID) region during actual recording. This is because physical addressesare needed for recording data and more reliable addressing is achieved.However, repeatedly recording the layer information results in overheadaccording to high density recording.

Thus, it is highly desirable to have a dual layer disc as a recordableand/or reproducible optical disc and to effectively record informationother than user data for high density recording.

SUMMARY OF THE INVENTION

To solve the above problems, it is an object of the present invention toprovide an optical disc having first and second recording layers onwhich a physical address of smallest recording units and an address ofthe smallest recording units recorded while recording on the disc arerecorded, and a method of identifying a recording layer by using anincrease or decrease in the physical address and the recorded address.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

Accordingly, to achieve the above and other objects of the invention,the present invention provides an optical disc comprising first andsecond recording layers on which data are recordable and/orreproducible, the first and second recording layers having a same trackspiral direction, wherein a physical address of smallest recording unitsincreases or decreases together with an address of the smallestrecording units recorded while recording on the disc, from an innerradius of the first recording layer to an outer radius of the firstrecording layer.

On the second recording layer, the physical address increases ordecreases together with the recorded address from an inner radius of thesecond recording layer to an outer radius of the second recording layer.

The present invention also provides an optical disc comprising first andsecond recording layers on which data are recordable and/orreproducible, the first and second recording layers having a same trackspiral direction, wherein an address of smallest recording unitsrecorded while recording the disc decreases as a physical address of thesmallest recording units increases and the recorded address increases asthe physical address decreases, from an inner radius of the firstrecording layer to an outer radius of the first recording layer.

On the second recording layer, the physical address increases ordecreases together with the recorded address from an inner radius of thesecond recording layer to an outer radius of the second recording layer.

Alternatively, on the second recording layer, the recorded addressdecreases as the physical address increases and increases as thephysical address decreases, from an inner radius of the second recordinglayer to an outer radius of the second recording layer.

The present invention provides an optical disc comprising first andsecond recording layers on which data are recordable and/orreproducible, the first and second recording layers having oppositetrack spiral directions, wherein a physical address of smallestrecording units increases or decreases together with an address of thesmallest recording units recorded during recording on the disc.

The present invention also provides an optical disc comprising first andsecond recording layers on which data are recordable and/orreproducible, the first and second recording layers having oppositetrack spiral directions, wherein, on the first recording layer, anaddress of smallest recording units recorded while recording data on thedisc decreases as a physical address of the smallest recording unitsincreases and increases as the physical address decreases.

On the second recording layer, the physical address increases ordecreases together with the recorded address.

The present invention also provides a method of identifying a recordinglayer on an optical disc comprising first and second recording layers onwhich data are recordable and/or reproducible, the first and secondrecording layers having the same track spiral direction. The methodcomprises assigning first smallest recording units on the firstrecording layer a physical address which is different from a physicaladdress of second smallest recording units on the second recordinglayer.

To achieve the above and other objects, an optical disc comprises atleast two recording layers on which data are recordable and/orreproducible, wherein a physical address of smallest recording units andan address of the smallest recording units recorded during recordingdata on the disc increase or decrease on the at least two recordinglayers. Alternatively, the physical address and the recorded addressincrease or decrease in different ways for each of the at least tworecording layers. The at least two recording layers may have the sametrack spiral direction or alternately may have opposite track spiraldirections.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail embodiments thereof with referenceto the accompanying drawings in which:

FIG. 1A schematically shows spiral directions of a parallel spiral trackoptical disc;

FIG. 1B illustrates an example in which sector addresses are recorded ina conventional optical disc for reproduction;

FIG. 1C shows changes in the rotation speed of a disc and reproductiondirection with respect to a radius of the disc where reproducing datafrom a conventional optical disc for reproduction;

FIG. 2A schematically shows spiral directions of an opposite spiraltrack optical disc;

FIG. 2B illustrates another example in which sector addresses arerecorded in a conventional optical disc for reproduction;

FIG. 2C shows changes in the rotation speed of a disc and reproductiondirection with respect to a radius of the disc where reproducing datafrom a conventional optical disc for reproduction;

FIGS. 3A-3D graphically show a first set of directions in which physicaladdresses and addresses recorded during recording increase or decreasein a parallel spiral track optical disc according to a first embodimentof the present invention;

FIGS. 4A-4D graphically show a second set of directions in whichphysical addresses and addresses recorded during recording increase ordecrease in a parallel spiral track optical disc according to the firstembodiment of the present invention;

FIGS. 5A-5D graphically show a third set of directions in which physicaladdresses and addresses recorded during recording increase or decreasein a parallel spiral track optical disc according to the firstembodiment of the present invention;

FIGS. 6A-6D graphically show a fourth set of directions in whichphysical addresses and addresses recorded during recording increase ordecrease in a parallel spiral track optical disc according to the firstembodiment of the present invention;

FIGS. 7A-7D graphically show a set of directions in which physicaladdresses and addresses recorded during recording increase or decreasein an opposite spiral track optical disc according to a secondembodiment of the present invention; and

FIGS. 8A-8D graphically show a set of directions in which physicaladdresses and addresses recorded during recording increase or decreasein an opposite spiral track optical disc according to a third embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

An optical disc according to the present invention is a recordableand/or reproducible disc having first and second recording layers L0 andL1. The first and second recording layers L0 and L1 have physicaladdresses of smallest recording units and addresses of the smallestrecording units recorded during recording (recorded addresses).

An optical disc according to a first embodiment of the present inventioncomprises a parallel spiral track optical disc in which first and secondrecording layers L0 and L1 have the same spiral direction. In theparallel spiral track optical disc, a physical address P1 and an addressR1 recorded while recording to the disc (hereinafter called “recordedaddress R1”) increase or decrease from an inner radius Rin of the firstrecording layer L0 to an outer radius Rout of the first recording layerL0, while a physical address P2 and an address R2 recorded whilerecording to the disc (hereinafter called “recorded address R2”)continuously increase or decrease from an inner radius Rin of the secondrecording layer L1 to an outer radius Rout of the second recordinglayer.

Referring to FIGS. 3A-3D, in a first arrangement of the firstembodiment, the first and second recording layers L0 and L1, thephysical addresses P1 and P2 increase or decrease together with therecorded addresses R1 and R2, respectively. That is, the physicaladdress P1 increases or decreases together with the recorded address R1in the first recording layer L0 and the physical address P2 increases ordecreases together with the recorded address R2 in the second recordinglayer L1.

In a second arrangement of the first embodiment, as shown in FIGS.4A-4D, the physical address P1 increases or decreases together with therecorded address R1 in the first recording layer L0 and the recordedaddress R2 decreases as the physical address P2 increases and therecorded address R2 increases as the physical address P2 decreases, inthe second recording layer L1. That is, as shown in an example of FIG.4A, the physical address P1 increases together with the recorded addressR1 from the inner radius Rin of the first recording layer L0 to theouter radius Rout and the physical address P2 increases and the recordedaddress R2 decreases from the inner radius Rin of the second recordinglayer L1 to the outer radius Rout.

In a third arrangement of the first embodiment, as shown in FIGS. 5A-5D,the recorded address R1 decreases as the physical address P1 increasesand the recorded address R1 increases as the physical address P1decreases, in the first recording layer L0 and the physical address P2increases or decreases together with the recorded address R2 in thesecond recording layer L2. That is, as shown in examples of FIGS. 5A and5B, the physical address P1 increases and the recorded layer R1decreases from the inner radius Rin of the first recording layer L0 tothe outer radius Rout, while the physical address P2 increases (FIG. 5A)or decreases (FIG. 5B) together with the recorded address R2 from theinner radius Rin of the second recording layer L1 to the outer radiusRout.

In a fourth arrangement of the first embodiment, as shown in FIGS.6A-6D, the recorded address R1 increases as the physical address P1decreases or the recorded address R1 decreases as the physical addressP1 increases, in the first recording layer L0, and the recorded addressR2 decreases as the physical address P2 increases or the recordedaddress R2 increases as the physical address P2 decreases, in the secondrecording layer L1.

For example, as shown in FIG. 6A, the physical address P1 decreases andthe recorded address R1 increases from the inner radius Rin of the firstrecording layer L0 to the outer radius Rout and the physical address P2increases and the recorded address R2 decreases from the inner radiusRin of the second recording layer L1 to the outer radius Rout.

In another example, as shown in FIG. 6B, the physical address P1decreases and the recorded address R2 increases from the inner radiusRin of the first recording layer L0 to the outer radius Rout and thephysical address P2 decreases and the recorded address R2 increases fromthe inner radius Rin of the second recording layer L1 to the outerradius Rout of the second recording layer. In the examples describedabove, the physical addresses P1 and P2 are recordable by pits at afront portion of the smallest recording unit. Alternatively, thephysical addresses P1 and P2 are recordable in a form of a wobble on thetrack.

Opposite spiral track optical discs according to second and thirdembodiments of the present invention, each comprising first and secondrecording layers L0 and L1 having opposite spiral directions, will nowbe described.

Referring now to FIGS. 7A-7D, an opposite spiral track optical discaccording to the second embodiment of the present invention is arecordable and/or reproducible disc having first and second recordinglayers L0 and L1. In the second embodiment a physical address P1 and arecorded address R1 increase or decrease from an inner radius Rin of thefirst recording layer L0 to an outer radius Rout of the first recordinglayer L0 and a physical address P2 and a recorded address R2continuously increase or decrease from an outer radius Rout of thesecond recording layer L1 to an inner radius Rin of the second recordinglayer.

Referring now to FIGS. 8A-8D, an opposite spiral track optical discaccording to a third embodiment of the present invention is a recordableand/or reproducible disc having first and second recording layers L0 andL1. In the third embodiment, a physical address P1 and a recordedaddress R1 increase or decrease from the outer radius Rout of the firstrecording layer L0 to the inner radius Rin while a physical address P2and a recorded address R2 continuously increase or decrease from theinner radius Rin of the second recording layer L1 to the outer radiusRout.

All arrangements applied to the parallel spiral track optical discaccording to the first embodiment of the present invention are alsoapplicable to the opposite spiral track optical discs according to thesecond and third embodiments of the invention. First, in the firstopposite spiral track optical disc, the physical address P1 increases ordecreases together with the recorded address R1 from the inner radiusRin of the first recording layer L0 to the outer radius Rout, while thephysical address P2 increases or decreases together with the recordedaddress R2 from the outer radius Rout of the second recording layer L1to the inner radius Rin. For example, as shown in FIG. 7A, the physicaladdress P1 increases with the recorded address R1 from the inner radiusRin of the first recording layer L0 to the outer radius Rout, while thephysical address P2 increases together with the recorded address R2 fromthe outer radius Rout of the second recording layer L1 to the innerradius Rin.

In the opposite spiral track optical disc according to the secondembodiment of the present invention, the physical address P1 increasesor decreases together with the recorded address R1 from the outer radiusRout of the first recording layer L0 to the inner radius Rin and thephysical address P2 increases or decreases together with the recordedaddress R2 from the inner radius Rin of the second recording layer L1 tothe outer radius Rout, corresponding to the increase or decrease of thephysical address P1 and the recorded address R1, respectively. Forexample, as shown in FIG. 8A, the physical address P1 increases togetherwith the recorded address R1 from the outer radius Rout of the firstrecording layer L0 to the inner radius Rin and the physical address P2increases together with the recorded address R2 from the inner radiusRin of the second recording layer L1 to the outer radius Rout.

In the opposite spiral track optical disc according to the secondembodiment, the physical address P1 increases or decreases together withthe recorded address R1 from the inner radius Rin of the first recordinglayer L0 to the outer radius Rout and the recorded address R2 decreasesas the physical address P2 increases and the recorded address R2increases as the physical address P2 decreases, from the outer radiusRout of the second recording layer L1 to the inner radius Rin. Forexample, as shown in FIG. 7B, the physical address P1 increases togetherwith the recorded address R1 from the inner radius Rin to the outerradius Rout and the physical address P2 increases and the recordedaddress R2 decreases from the outer radius Rout of the second recordinglayer L1.

Similarly, in the opposite spiral track optical disc according to thethird embodiment, the physical address P1 may increase or decreasetogether with the recorded address R1 from the outer radius Rout of thefirst recording layer L0 to the inner radius Rin and the recordedaddress R2 decreases as the physical address P2 increases and therecorded address R2 increases as the physical address P2 decreases, fromthe inner radius Rin of the second recording layer L1 to the outerradius Rout. An example thereof is shown in FIG. 8B.

Further, in the opposite spiral track optical disc according to thesecond embodiment, the recorded address R1 may decrease as the physicaladdress P1 increases and increase as the physical address P1 decreases,from the inner radius Rin of the first recording layer L0 to the outerradius Rout. On the other hand, the physical address P2 may increase ordecrease together with the recorded address R2 from the outer radiusRout of the second recording layer L1 to the inner radius Rin. Anexample thereof is shown in FIG. 7C.

Similarly, in the opposite spiral track optical disc according to thethird embodiment, the recorded address R1 may decrease as the physicaladdress P1 increases or increase as the physical address P1 decreases,from the outer radius Rout of the first recording layer L0 to the innerradius Rin. On the other hand, the physical address P2 may increase ordecrease together with the recorded address R2 from the inner radius Rinof the second recording layer L1 to the outer radius Rout. An examplethereof is shown in FIG. 8C.

In the opposite spiral track optical disc according to the secondembodiment, as shown in FIG. 7D, the recorded address R1 may decrease asthe physical address P1 increases and increase as the physical addressP1 decreases, from the inner radius Rin of the first recording layer L0to the outer radius Rout. At the same time, the recorded address R2decreases as the physical address P2 increases and increases as thephysical address P2 decreases, from the outer radius Rout of the secondrecording layer L1 to the inner radius Rin.

In the opposite spiral track optical disc according to the thirdembodiment, as shown in FIG. 8D, the recorded address R1 decreases asthe physical address P1 increases and increases as the physical addressP1 decreases, from the outer radius Rout of the first recording layer L0to the inner radius Rin. At the same time, the recorded address R2decreases as the physical address P2 increases and increases as thephysical address P2 decreases, from the inner radius Rin of the secondrecording layer L1 to the outer radius Rout.

Where the parallel spiral track optical disc is compared with theopposite spiral track optical discs of the second and third embodiments,the opposite spiral track optical discs of the second and thirdembodiments differ from the parallel spiral track optical disc of thefirst embodiment in that the direction in which the physical address P1or the recorded address R1 provided to the first recording layer L0increases or decreases is opposite to that in which the correspondingphysical address P2 or the recorded address R2 provided to the secondrecording layer L1 increases or decreases. The same is true of thearrangement of physical addresses and recorded addresses made dependingon an increase or a decrease in the addresses in the opposite spiraltrack optical discs according to the second and third embodiments. Thus,all arrangements in the parallel spiral track optical disc according tothe first embodiment of the present invention are applicable to theopposite spiral track optical discs according to the second and thirdembodiments, and thus detailed descriptions thereof will be omitted.

Furthermore, the arrangements of physical addresses and recordedaddresses described above are applicable to an optical disc having twoor more recording layers. That is, a physical address and a recordedaddress increase or decrease for each recording layer in the opticaldisc having two or more recording layers. Thus, an increase or decreasein a physical address and a recorded address for each recording layerare combinable in various ways. Here, the two or more recording layersmay have the same track spiral direction or alternately have oppositetrack spiral directions.

All possible cases where physical addresses and recorded addresses infirst and second recording layers are arrangeable according to anincrease or decrease in the addresses and the direction in which such anincrease or decrease is made are represented by ordered pairs. Here, thefirst and second recording layers are represented by 1 and 2,respectively, physical and recorded addresses are represented by P andR, respectively, and an increase and a decrease in those addresses arerepresented by i and d, respectively. For example, {(1Pi,1Ri) (2Pi,2Ri)}refers to a case in which physical addresses P and recorded addresses Ron the first and second recording layers 1 and 2 all increase, as shownbelow:

-   {(1Pi,1Ri) (2Pi,2Ri))} {(1Pi,1Ri) (2Pd,2Rd)}-   {(1Pd,1Rd) (2Pi,2Ri)} {(1Pd,1Rd) (2Pd,2Rd)}-   {(1Pi,1Ri) (2Pi,2Rd)} {(1Pi,1Ri) (2Pd,2Ri)}-   {(1Pd,1Rd) (2Pi,2Rd)} {(1Pd,1Rd) (2Pd,2Ri)}-   {(1Pi,1Rd) (2Pi,2Ri)} {(1Pi,1Rd) (2Pd,2Rd)}-   {(1Pd,1Ri) (2Pi,2Ri)} {(1Pd,1Ri) (2Pd,2Rd)}-   {(1Pd,1Ri) (2Pi,2Rd)} {(1Pd,1Ri) (2Pd,2Ri)}-   {(1Pi,1Rd) (2Pi,2Rd)} {(1Pi,1Rd) (2Pd,2Ri)}-   {(1Pi,1Rd) (2Pd,2Ri)} {(1Pd,1Ri) (2Pd,2Ri)}

The above arrangements may be applied to the recordable parallel spiraltrack disc according to the first embodiment and the opposite spiraltrack discs according to the second and third embodiments. The physicaladdresses P1 and P2 may be recorded in the form of pits at the front ofeach smallest recording unit or may be recorded in the form of a wobbleon a track.

A method of identifying recording layers on a recordable and/orreproducible optical disc having first and second recording layers L0and L1 according to the present invention will now be described. Themethod of identifying recording layers according to the presentinvention on an optical disc comprises making an increase or decrease inphysical addresses P1 and P2 on the first and second recording layers L0and L1 different. That is, the first and second recording layers L0 andL1 are identified by increasing the physical address P1 on the firstrecording layer L0 while decreasing the physical address P2 on thesecond recording layer L1, or by decreasing the physical address P1 onthe first recording layer L0 while increasing the physical address P2 onthe second recording layer L1. The present invention uses an increase ordecrease in a physical address to identify a recording layer, therebyallowing for the effective use of a user data area since there is noneed to separately record information about the recording layer.

An optical disc according to the present invention provides a dual layerdisc having first and second recording layers L0 and L1 on which dataare recordable and eraseable, and from which data are reproducible, inorder to meet a strong demand for high density optical discs.Furthermore, the method of identifying recording layers on an opticaldisc according to the present invention allows recording layers to beidentified by making increases or decreases in physical addresses in therecording layers different. This eliminates a need to repeatedly recordinformation about the recording layers and thus increases the effectiveuse of a user data area.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A method of recording data to an optical disc comprising first andsecond recording layers, the method comprising: identifying a recordinglayer to be recorded as being either the first or the second recordinglayer according to whether recording addresses of smallest recordingunits recorded while recording data on the disc decrease as physicaladdresses of the smallest recording units increase or increase as thephysical addresses decreases so as to distinguish between the first andsecond recording layers, and recording data to the identified recordinglayer.
 2. The method of claim 1, wherein the physical address isrecorded in a form of pits at a front portion of each smallest recordingunit.
 3. The method of claim 1, wherein the physical address is recordedon a track in a form of a wobble.
 4. A method of recording data on anoptical disc having first and second recording layers, the methodcomprising: detecting addresses in respective front portions of smallestrecording units of the first and second recording layers to detect firstand second trends, the recording addresses and corresponding physicaladdresses of the first recording layer varying together according to adirection of travel on the disc to define the first trend, and therecording addresses and corresponding physical addresses of the secondrecording layer varying together according to the direction of travel todefine the second trend; identifying a recording layer as being thefirst recording layer if the first trend is detected and recording thedata from the identified first recording layer; and identifying arecording layer as being the second recording layer if the second trendis detected and recording the data from the identified second recordinglayer.
 5. The method of claim 4, wherein the recording and physicaladdresses of the first recording layer and the recording and physicaladdresses of the second recording layer all increase or all decreasetogether.
 6. The method of claim 4, wherein: the recording and physicaladdresses of the first recording layer increase together; and therecording and physical addresses of the second recording layer decreasetogether.
 7. The method of claim 4, wherein: the recording and physicaladdresses of the first recording layer decrease together; and therecording and physical addresses of the second recording layer increasetogether.
 8. A method of recording data to an optical disc having firstand second recording layers, the method comprising: identifying arecording layer to be recorded as being either the first or the secondrecording layer according to a detected trend of recording addresses inrespective front portions of smallest recording units of the first andsecond recording layers, the recording addresses and the physicaladdresses of one of the first and second recording layers varyingaccording to a direction of travel along the disc, and the recordingaddresses and the physical addresses of the other of the first andsecond recording layers varying oppositely according to the direction oftravel; and recording data to the identified recording layer.
 9. Themethod of claim 8, wherein: the recording and physical addresses of thefirst recording layer vary together, and the recording and physicaladdresses of the second recording layer vary oppositely.
 10. The methodof claim 8, wherein: the recording and physical addresses of the secondrecording layer vary together, and the recording and physical addressesof the first recording layer vary oppositely.
 11. A method of recordingdata to an optical disc having first and second recording layers, themethod comprising: identifying a recording layer as being either thefirst or second recording layer according to a detected trend of arecording addresses in respective front portions of smallest recordingunits of the first and second recording layers, wherein the recordingaddresses and the physical addresses of one of the first and secondrecording layers vary oppositely according to a direction of travelalong the disc, and the recording addresses and the physical addressesof the other of the first and second recording layers vary oppositelyaccording to the direction of travel along the disc; and recording datato the identified recording layer.